Equilibrium charge-fractions for H+ and H2+ ions transmitted through carbon foils at 60-300 keV

Charge-fractions have been measured for H+ and H2+ ion beams transmitted through thin (5-15 mu gcm-2) carbon foils. The results for H+ ions show complete equilibration and agree with existing published data. The H2+ beams show almost total dissociation at all energies studied. The measured charge fractions differ significantly from those of H+ beams having the same velocity, and show a foil thickness dependence even after correcting for energy losses in the foils. This is interpreted as a spatial correlation effect, due to the close proximity of the break-up atoms from each H2+ ion as they leave the foil.